if funct2&^3 != 0 {
		panic("encodeR4: funct2 requires more than 2 bits")
	}
	return rs3<<27 | funct2<<25 | rs2<<20 | rs1<<15 | enc.funct3<<12 | funct3<<12 | rd<<7 | enc.opcode
}

func encodeRII(ins *instruction) uint32 {
	return encodeR(ins.as, regI(ins.rs1), 0, regI(ins.rd), ins.funct3, ins.funct7)
}

func encodeRIII(ins *instruction) uint32 {